An implantable device such as a stent graft can include a exposed self expanding stent which in use can expand and engage against the wall of a vessel such as the aorta and assist in retaining the implantable device in its desired position. Such an exposed self expanding stent can include barbs to assist with engagement and retention in the desired position. During introduction it is necessary to keep the exposed stent in a contracted condition and for this purpose a stent graft delivery device can include a capsule into which the exposed stent is received. The capsule also prevents the barbs from premature engagement with a vessel wall.
U.S. Pat. No. 7,435,253 issued on Oct. 14, 2008 and entitled “Prosthesis and a Method of Deploying a Prosthesis” discloses a stent graft introducer incorporating a capsule retention system and the teachings therein are incorporated herein in their entirety.
Premature release of the exposed stent from the capsule could cause problems to a patient and hence there has been proposed a trigger wire release system using a thin stainless steel wire which extends from a distal end of an introduction device and engages a proximal bend of the exposed stent inside the capsule.
It is desirable to use thinner and more flexible trigger wires but the prior art arrangements for trigger wire release system are not suitable with more flexible wires.
It is the object of this disclosure to provide a improved exposed stent retention system or at least provide a physician with a useful alternative device.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis means the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.